Illumination device for product examination via pulsed illumination

ABSTRACT

An illumination device for use with a product inspection machine inspecting products according to at least one characteristic using pulsed illumination for inspection in two wavelengths. The invention includes a plurality of arrays of semiconductor light sources from which a wavelength may be selected, either specifically or by combination of specific semiconductor light sources, for impinging on passing product and at least one array of semiconductor light sources from which the same wavelength may be selected and which provides intensity equal to the plurality of arrays impinging on a background surface for detection and comparison.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. patent application Ser. No.11/564,622, Illumination Device for Product Examination, filed Nov. 29,2006.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a product illumination device forexamination of passing product wherein multiple wavelengths andintensities may be selected, and particularly for use in for productsorting where two or more wavelengths are to be detected by a singlephotodetector.

2. Description of the Related Art

A typical sorting machine of the type with which the present inventionis used is a high-speed sorting machine for use with small products,including fungible products in the food and pharmaceutical industries.As used herein, product refers not only to a manufactured good but alsoto component items from which production of a good may be accomplished.As a result, the invention may also be used in conveyor sortingmachines, for sorting of other flowing materials, such as plasticpellets and ammunition, and for quality control examination of product.

For example, individual rice grains may be sorted in a gravity-fedsorter to separate grains selected as “substandard.” In the art,“substandard” may apply to a grain having any undesirablecharacteristic, including reflected wavelength (color), shape, size orbreakage, or any other characteristic not within the limits foracceptable products for a particular sorting. Alternative feed systems,such as belt driven conveyors, are also well-known in the art.Alternatively, certain rarer products may be desirable and thereforedeflected from the flow of the less rare and less desirable remainingproducts. Likewise other materials may be sorted from the product flow,including, such as in the case of harvested goods, non-product materialssuch as glass, rocks, sticks and bran.

Sorting machines may employ one or more optical sensors to differentiatebased on reflected wavelength, size, moisture content or othercharacteristics as determined in radiation bands, which may be within oroutside the visible light spectrum. When such sorting is accomplished byuse of two radiation bands, the sorting procedure is referred to asbichromatic sorting. In bi-chromatic sorters, a combination of filters,typically red/green and red/blue, has been required to limit thewavelengths and/or intensity impinging on the product. Such a systemrequires significant disassembly, and therefore lost productivity, whenany change to the wavelengths and/or intensity is desired. Such a changemay be desired if a different product is to be sorted or if a differentcharacteristic is selected for sorting.

Optical sorting machines of the type employ optical sensors that includemultiple photodetectors, such as a charged-couple device and photodiodearrays. The photodetectors are positioned to observe the illuminatedproduct stream through a light-penetrating window. The product streamtypically passes between an optical sensor and a background, where thebackground matches the product stream in standard reflected wavelengthso that only a variation in a product's reflected wavelength causes adetection event. The illumination is from one or more light sourcesdirected at the product stream to cause standard reflectivity ortransmission (transluminence) from standard products in the radiationbands being observed and to cause nonstandard reflectivity fromnonstandard products in those bands.

One of the main components of such a sorting system is the illuminationassembly. The illumination assembly provides a starting point for thereception quality of the vision system. Typically, the assembly isrequired to supply a uniform light supply and have a high intensity atthe object point (sometimes referred to as the scanline) of the visionsystem. Most inspection systems include some sort of illuminator.Conventional illuminators include incandescent and fluorescent lamps andlight emitting diodes. Various optical arrangements have been designedfor better illumination, such as ringed lamp arrays, focused filamentprojectors, and fiber optic emitters. These include attempts to avoiduneven illumination which may result in detection of shadows as defects.

These prior art illumination sources present certain difficulties. Toadjust the wavelength or wavelengths of light and the light intensityimpinging on passing product, prior art teaches the use of filters,typically mounted adjacent the camera. The prior art is prone to wasteenergy as heat, rather than light, which must then be removed from thesorting machine. Moreover, the combining color band in a monochromaticapplication is limited.

Such sorting machines also include one or more ejector mechanismslocated downstream of the sensor or sensors with multiple nozzlesassociated with one or more valves actuated by an electrical signalcoordinated with sensor detection. When a product having or lackingselected criteria is detected, an electrical signal is produced toactuate the valve of the ejector nozzle associated with the predictedlocation of the selected product at the predicted time the selectedproduct will pass the ejector. The time elapsed between the selectedproduct passing the sensor or sensors and the selected product beingejected is minimal to limit possible vertical and/or horizontaldeflection of the selected product upon contact with non-selectedproducts. Each ejector is therefore normally located as close aspossible to the plane at which the optical sensor or sensors reviews thepassing products, typically referred to as the scanline, ideally beingjust downstream therefrom and closely adjacent thereto.

It is desirable is such sorting machines to provide for productexamination under multiple wavelengths because product displays varyingreflection factors at particular wavelengths. For example, it isadvantageous to provide examination in the infrared region because therelative absorption and reflectance throughout the infrared spectrum isdependent upon the chemical composition and physical characteristics ofthe sample. Infrared illumination therefore provides additional datawhich may be used for sorting. Thus two or more different wavelengthsmay be utilized to produce data regarding two or more differentcharacteristics. Detection of multiple infrared wavelenths permits theuse of comparison algorithms that would otherwise not be available withdata for a single wavelength.

Problematically, use of more than one wavelength for detection haspresented various difficulties. A single photodetector is unable tosimultaneously detect multiple wavelengths, therefore, the prior artattempted use of multiple photodetectors. Use of multiple photodetectorsfor multiple wavelengths, however, presents its own difficulties. Giventhe close proximity of the product, the illumination source and thephotodetectors in the sorting machine, space is at a premium andpresents difficulties in providing space to position and direct aphotodetector for each wavelength to a single scanline on a common ornear common plane. Moreover, it is difficult to align multiplephotodetectors to a common scanline and to maintain that alignment overtime. Finally, photodetectors are costly, thus the use of multiplephotodetectors is a disincentive to the use of multiple wavelengths.

Depending on the product to be sorted and the characteristic orcharacteristics selected as the basis for sorting, a particularwavelength, or wavelengths, and intensity, or intensities, of light maybe desirable for characteristic identification. In convention productsorting machines, such a change may require replacement of the existingillumination assembly, thereby requiring the sorting machine to beremoved from service until filters or light sources are altered orexchanged.

It would be an improvement over the prior art to provide an illuminationdevice that provides intense, consistent illumination of the products tobe viewed along a linear or elongated scan line, thereby providingconsistent identification of selected characteristics and substantiallyreducing mischaracterization of products as having occlusions or otherdefects actually caused by shadows.

Additionally, it would be an improvement to the prior art to provide anillumination device that may instantaneously adjust the wavelength orwavelengths and/or wavelength intensity impinging on passing product.

It would be a further improvement to the prior art to provide anillumination device that may be used to detect multiple wavelengths by asingle photodetector.

It would be a further improvement to the prior art to provide anillumination device that reduces the need to remove a sorting machinefrom service to alter the wavelengths used for sorting.

SUMMARY OF THE INVENTION

It is therefore a principle object of the present invention to providean illumination device that may instantaneously, and withoutdisassembly, adjust both the wavelengths and intensity impinging onpassing product and which may detect multiple wavelengths using a singlephotodetector

The present invention comprises an illumination assembly for a machinevision viewer for a product sorting machine that provides a flow ofobjects along a horizontal scanline. The present invention includes ahorizontally-disposed product illumination assembly with a plurality ofsemiconductor light sources in repeated patterns according to theirwavelength emission, which may be light-emitting diodes, of one or morewavelengths mounted thereon, and a corresponding horizontally-disposedbackground surface illuminated by a plurality of sequenced semiconductorlight sources of one or more wavelengths. Moreover, the intensity of anyemitted wavelength or wavelengths may be adjusted to further vary thewavelength impinging on passing product and the corresponding backgroundsurface against which the product is imaged for sorting. For eachphotodetector utilized to detect in a wavelength range, for example thevisible and infrared spectrums, a plurality of separate wavelengths, inthis example a visible and a infrared wavelength, are rapidly andseparately emitted. The received data may then be analyzed for theseparate wavelengths.

The illumination device includes a passage between a productillumination assembly and the background assembly through which productto be sorted passes. A linear viewport, parallel to thehorizontally-disposed product illumination assembly, is provided for oneor more photodetectors to receive data pertaining to each productpassing between the product illumination assembly and the backgroundassembly for identification of any product having a characteristic foundin the minority of product. An ejector is positioned adjacent theillumination device.

The illumination device may employ a pair of product illuminationassemblies, wherein a background assembly is integrated into eachproduct illumination assembly. The two product illumination assembliesare then oriented in parallel such that a photodetector imaging throughthe linear viewport of the first product illumination assembly imagesthe opposing background surface in the absence of product.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the described features, advantages andobjects of the invention, as well as others which will become apparent,are attained and can be understood in detail, more particulardescription of the invention briefly summarized above may be had byreference to the embodiments thereof that are illustrated in thedrawings, which drawings form a part of this specification. It is to benoted, however, that the appended drawings illustrate only a typicalpreferred embodiment of the invention and are therefore not to beconsidered limiting of its scope as the invention may admit to otherequally effective embodiments.

FIG. 1 depicts a side view of a typical sorting machine known in the artincluding the illumination device of the present invention.

FIG. 2 depicts a simplified side view of a typical machine viewingsystem known in the art.

FIG. 3 depicts a cross-sectional view of the illumination device of thepresent invention and an associated photodetector.

FIG. 4 depicts a cross-sectional view of the illumination device of thepreferred embodiment of the present invention and an associatedphotodetector.

FIG. 5 depicts a perspective view of a section of one half of theillumination device of the preferred embodiment of the present inventionand an associated photodetector.

FIG. 6 depicts a perspective view of an entire one half of theillumination device of the preferred embodiment of the presentinvention.

FIG. 7 depicts the front of one half of the illumination device of thepreferred embodiment.

FIG. 8 depicts a perspective view of the rear of one half of theillumination device of the preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIG. 1, a typical product-sorting machine includingthe illumination device of the present invention is depicted. Theproduct-sorting machine 10 includes a hopper 16, a feeder 18, a slide12, a vision system 20, and an ejector 26. The components of typicalproduct sorting machine 10 are illustrated in FIG. 2, including acontainer 28 for segregated products and a bin 30.

The products to be viewed and sorted by the typical product-sortingmachine 10 are retained in hopper 16 and are ultimately dispensed ontoslide 12 by feeder 18. Feeder 18 may be of any type commonly known inthe art, such as a conveyor or a vibratory feeder. In the exemplaryproduct-sorting machine 10, momentum is imparted to the product to besorted by the product conveyor 14, which may be a gravity slide 12 orbelt conveyor. Prior to the product passing before vision system 20,product conveyor ceases to support the product, directing the productalong trajectory 32. The product sorting machine 10 of the embodimentdisclosed in FIGS. 1 and 2 provides for free fall of the products pastslide 12.

The product to be sorted may be any of a plurality of organic orinorganic objects, such as, for example, grains, nuts, and plasticpellets. The products may be viewed and sorted based on various criteriadetermined by the user, including size, color, defects and othercharacteristics.

Referring to FIG. 3, vision system 20 includes an illumination device100 that is composed of a horizontally disposed product illuminationassembly 200 and a corresponding horizontally-disposed backgroundassembly 300, a photodetector 400, and an ejector 500. In free fall, theproduct passes the first, or upper edge, of illumination device 100 usedin conjunction with vision system 20, and the second, or lower edge, ofillumination device 100. In operation, as a continuous flow of productpasses through product-sorting machine 10 and therefore pastillumination device 100, illumination device 100 provides illuminationof the flow of passing product. Horizontally-disposed productillumination assembly 200 and a corresponding horizontally-disposedbackground assembly 300 are positioned in opposition sufficientlydistant to ensure product being directed from conveyor 14, in particularby slide 12, passes therethrough without interference.

A photodetector 400 is positioned to image product passing betweenproduct illumination assembly 200 and background assembly 300.Photodetector 400 has a vertical field of vision. The point at whichproduct passes from the first edge to the second edge of illuminationdevice 100 between product illumination assembly 200 and backgroundassembly 300 and before photodetector 400 is identified as scanline 700.Scanline 700 is of sufficient height to image passing product. To theextent product is less than the height of the scanline 700,photodetector 400 images background surface 302, which is aligned withphotodetector 400 and scanline 700. Photodetector 400 images scanline700 through product illumination assembly 200 via viewport 202. Toincrease the effectiveness of photodetector 400, product is illuminatedat scanline 700.

To reduce contrast between acceptable product reflecting illuminationfrom product illumination assembly 200 and background surface 302,background surface 302 is illuminated from within background assembly300 consistent with the wavelength, or wavelengths, and intensity, orintensities, of product illumination assembly 200. Background surface302 is of sufficient height and position to include the arc or chordlength of the field of vision of photodetector 400 passing throughviewport 202 and scanline 700 at the inner surface 303 of backgroundassembly 300.

It is preferred that product be as completely imaged, particularly bothfront and back, as possible for sorting. To that extent, in thepreferred embodiment, background assembly 300 is integrated into productillumination assembly 200, as depicted as background assembly 600 inFIG. 4, and two product illumination assemblies 200 are utilized.

As depicted in FIGS. 3-7, each product illumination assembly 200includes a first semiconductor-light-source product-illuminating array204 of semiconductor light sources 208, and a secondsemiconductor-light-source product-illuminating array 206 ofsemiconductor light sources 208. Semiconductor light sources includelighting emitting diodes (LEDs), laser diodes, organic LEDs, and anyother semiconductor light source. Semiconductor light source refers tolighting devices that utilize semiconductors as a light source and notnecessarily the semiconductor itself. Likewise light source refers to asource of radiant energy in the visible and invisible light spectrums.First semiconductor-light-source product-illuminating array 204 andsecond semiconductor-light-source product-illuminating array 206 arepositioned sufficiently distant scanline 700 to ensure the light of eachactivated semiconductor light source of first semiconductor-light-sourceproduct-illuminating array 204 and each activated secondsemiconductor-light-source product-illuminating array 206 sufficientlyblend to provide uniform illumination of scanline 700. In the preferredembodiment, first semiconductor-light-source product-illuminating array204 and second semiconductor-light-source product-illuminating array 206are affixed on supports 210. Supports 210 are angled to ensure thegreatest illuminance of scanline 700 from firstsemiconductor-light-source product-illuminating array 204 and secondsemiconductor-light-source product-illuminating array 206. Illuminanceis the total amount of visible light illuminating (incident upon) apoint on a surface from all directions above the surface. This “surface”can be a physical surface or an imaginary plane. Supports 210 must besufficiently located so as not interfere with photodetector 400.

Likewise, as depicted in FIG. 3 with respect to background assembly 300,and in FIGS. 4-7 with respect to background assembly 600 at least asingle semiconductor light source background illuminating array 604 ofsemiconductor light sources 208, which may be light-emitting diodes.Semiconductor light source background illuminating array 604 ispositioned sufficiently distant background 302 to ensure the light ofeach semiconductor light source 208 of the semiconductor light sourcebackground illuminating array 604 sufficiently blends to provide uniformillumination of background 302. In the preferred embodiment,semiconductor light source background illuminating array 604 is affixedon support 610. Support 610 is angled to ensure the illuminance ofbackground 302 consistent with scanline 700 from semiconductor lightsource background illuminating array 604. Support 610 must besufficiently located so as not interfere with photodetector 400. Asecond array of semiconductor light sources may be located oppositesemiconductor light source background illuminating array 604.

Alternatively, supports 210 may be altered such that each semiconductorlight source array may be relocated within illumination device 100 andthe light from each array redirected, by prisms or mirrors, to properlyilluminate scanline 700 and background 302 (not shown). Various methodsto redirect light and to encourage blending of light sources are wellknown in the art.

In operation, each photodetector 400 is located above the horizontalcenterline of illumination device 100, views scanline 700 approximatelyat the center of illumination device 100, and views background 302 belowthe horizontal centerline 800. The wavelength(s) and intensity(ies)impinging product at scanline 700 from first semiconductor-light-sourceproduct-illuminating array 204 and second semiconductor-light-sourceproduct-illuminating array 206 are replicated on background 302 bysemiconductor light source background illuminating array 604 to providemaximum contrast of characteristics on passing product foridentification by photodetector 400 and therefore activation of ejector500.

First semiconductor-light-source product-illuminating array 204 iscomposed of a series of semiconductor light sources 208, which may be ofone or more wavelengths, including those in the visible and infraredspectrums. In circumstances where semiconductor light sources 208 infirst semiconductor-light-source product-illuminating array 204 are of aplurality of wavelengths, semiconductor light sources 208 cycle throughthe same sequence of light sources 208 throughout the array. Repetitionof light sources 208 ensures that the resulting wavelengths blend by thetime the light reaches scanline 700. Likewise, in circumstances wheresemiconductor light sources 208 of a plurality of wavelengths arearrayed on first semiconductor-light-source product-illuminating array204, a corresponding array of semiconductor light sources 208 are fixedfor second product-illuminating array 206 in a complementary sequence.For example, a sequence of red in the visible spectrum and green in thevisible spectrum semiconductor light sources 208 in firstsemiconductor-light-source product-illuminating array 204 would becomplemented by a sequence of green in the visible spectrum and red inthe visible spectrum semiconductor light sources 208 in secondsemiconductor-light-source product-illuminating array 204. In thepreferred embodiment, first semiconductor-light-sourcesproduct-illuminating array 204 is of a single color, such as red in thevisible spectrum, and second semiconductor-light-sourceproduct-illuminating array 206 is of a single color, such as blue in thevisible spectrum. Use of a consistent color semiconductor light sources208 per first and second array is preferred for ease of repair andmanufacture. The number of colors permissible in the assembly is aresult of the density of semiconductor light sources and distance fromscanline 700 or background 302.

Background array 604 complements both first semiconductor-light-sourcesproduct-illuminating array 204 and second semiconductor-light-sourcesproduct-illuminating array 204, such that if the color of firstsemiconductor-light-sources product-illuminating array 204 is red in thevisible spectrum, and the color of second semiconductor-light-sourcesproduct-illuminating array 206 is blue in the visible spectrum,background array 604 will constitute a combination of red and bluesemiconductor light sources.

As can be appreciated, the height of each product illumination assembly200 is limited to the minimum size practicable to contain at least twoarrays of semiconductor light sources 204, 206, a background surface 302sufficient height, the illumination for the background surface 302, andsufficient depth for the light emitted from the semiconductor lightsources 208 in the product illumination assembly 200 to converge andblend at the scanline 700 and for the light from the semiconductor lightsources 208 illuminating the background surface 302 to converge andblend on the background 302.

Various methods to promote convergence and blending of the light of thesemiconductor light sources 108, particularly light emitting diodes(LEDs), are well known in the art.

Use of semiconductor light sources of a plurality of wavelengthsprovides advantages over the prior art. The need for replacement oralteration of filters to obtain different wavelengths and intensitiesfor characteristic selection is eliminated. Likewise, in monochromaticsorting systems, multiple colors may be used to enhance the colordifference of the product having the characteristic to be deflected. Onbi-chromatic applications, there is no need to add a filter in front ofthe photodetector when using a simple dichroic mirror. Finally, eachchannel (semiconductor light source array) can be a combination ofcolors on hi-chromatic applications.

The illuminance on passing product and the background 302 may becontrolled by adjusting the intensity of semiconductor light sources 208contained in first semiconductor-light-source product-illuminating array204, second semiconductor-light-source product-illuminating array 206and background array 604. The intensity of each semiconductor lightsource 208 may be independently controlled to affect the intensity ofthe wavelength(s) emitted. Such control may be via a computer or otherdevice known in the art. Any variance in emitted intensity of anyparticular semiconductor light source 208 may be controlled to ensureconsistent intensity. Similarly, the intensity of all semiconductorlight sources 208 of a particular wavelength or wavelengths found infirst semiconductor-light-source product-illuminating array 204, secondsemiconductor-light-source product-illuminating array 206 and backgroundarray 604 may be commonly controlled and adjusted.

When separate wavelengths are utilized for product sorting, theillumination device 100 will illuminate passing product for a periodsufficient to permit capture of a satisfactory image, i.e. a pulse,before illuminating with another wavelength, i.e. another pulse, fromamong the wavelengths available with semiconductor light sources 208.Illumination device 100 is capable of pulsing at least once per secondand may be configured to pulse a plurality of times each second. Forexample, if a charge-coupled device is used as a photodetector, aduration of display at each wavelength equal or greater than the cameraintegration time, the time necessary for successive frames to beintegrated in the CCD camera to improve the signal to noise ratio in theimage, may be required. Moreover, when separate wavelengths are utilizedfor product sorting, the wavelengths need not be displayed or pulsed ina particular sequence. For example, a first wavelength may be displayed,followed by a second wavelength, a combination of the first and secondwavelengths, then the second wavelength again before the cycle beginsagain. The selection and sequence of various wavelengths may be adjustedbased on the product to be sorted and the desirability of data to beretrieved.

Illumination device 100 may be positioned perpendicular to trajectory 32of passing product, regardless of the trajectory's plane. Additionally,product illumination assembly 100, whether incorporating backgroundassembly 600 or mating with background assembly 300, may be fitted withheat sinks 900. Likewise, if background assembly 300 is used, it too maybe fitted with heat sinks 950. in operation, the heat from semiconductorlight sources 208 may be removed from illumination device 100 via suchheat sinks. Viewport 202 may be an opening, to additionally permit heatto exit, or may be sealed. The assemblies of product illuminationassembly 100, whether incorporating background assembly 600 or matingwith background assembly 300, may be sealed against passing product,preventing any contaminants from interfering with semiconductor lightsources 208 or background 302. Alternatively background assembly 300 maybe the lower of the two assemblies and may contain orifices (not shown)through which passing product not following trajectory 32 and insteadfalling to into background assembly 300 may exit.

The illumination device 100 disclosed herein provides additionaladvantages in operation. By constructing product illumination assembly200, and, if applicable, background assembly 300, as a single component,the component may be removed for service or replacement, rather thanrequiring removal of the individual assemblies. Such modularconstruction reduces the time required for repair or replacement andtherefore increases productivity of the sorting machine. Additionally,construction of illumination assembly 200, and, if applicable,background assembly 300, with pulsed illumination from light sourcesonto scanline 700 and background 302, also eliminates the need forinternal reflective surfaces such as mirrors. Moreover, use ofsemiconductor light sources sufficiently distant scanline 700 andbackground 302 likewise eliminates the need for any diffuser, therebyreducing the number of parts necessary to illuminate scanline 700 andbackground 302.

To further improve uniformity of pulsed illumination, illuminationdevice 100 may be constructed longer than the width of conveyer 14, orslide 12 if applicable. Thus, the effective area of illumination extendsto the full edge of the conveyor 14, or slide 12.

Referring to FIGS. 3 and 4, ejector 500 comprises a series of nozzles501 for selective intermittent ejection of compressed gas, fluid or air(not shown) into trajectory 32. Nozzles 501 are aligned parallel toscanline 700 adjacent trajectory 32, such that any individual product(not shown) identified to be sorted may be diverted to trajectory 32 bwithout diverting adjacent product.

In operation, upon flow of a quantity of products along trajectory 32through vision system 10, photodetector 400 outputs optical data inrelation to a product passing along scanline 700 and transmits such datato a processor for determination whether the acquired data is within arange of acceptable levels or outside such range. If the data is notwithin specific parameters, the particular nozzle or nozzles 501 ofejector 500 associated with the lateral position of the identifiedproduct is engaged to impart a force to the particular item as itpasses, thereby changing the trajectory of the identified product. Forillustration purposes, the trajectory of a rejected product is depictedas 32 b and the trajectory of a product that is not rejected is depictedas 32.

The machine vision system 10 of the present invention is useful in avariety of applications to identify measuring characteristics of aproduct. The high and relatively even intensity of pulsed illuminationwithin illumination device 100 at scanline 700 makes the presentinvention particularly useful in identifying flaws in transparentproducts, such as plastic pellets. In an application involving atransparent product such as a plastic pellet, a characteristic to bescanned, and upon which sorting is conducted, is the existence ofcontaminants in the product. Transparent products involve a lensingeffect wherein light variations exterior to the product may be reflectedby the product. The present invention minimizes such lensing effect inpart by limiting the light impinging on product and by controlling theone or more specific wavelengths and intensities detected forprocessing. Additionally, the plurality of semiconductor light sourcearrays within illumination device 100 ensures uniform wavelengths andintensities of light at scanline 700 and at background 302 forcomparison purposes.

Additionally, an opaque contaminant may be identified using theillumination device 100 of the present invention. A method ofdetermining an opaque contaminant is to determine the deviation of thetotal quantity of light intensity as measured at photodetector 400 asthe product passes through scanline 700. An opaque contaminant reflectsless light to photodetector 400 than a product that contains nocontaminant. The illumination device 100 of the present inventionproduces pulsed illumination levels at scanline 700 that are notdistorted by shadows created by uneven lighting and surfaceimperfections of the product to be scanned and sorted.

The foregoing disclosure and description of the invention isillustrative and explanatory thereof. Various changes in the details ofthe illustrated process may be made within the scope of the appendedclaims without departing from the spirit of the invention. The presentinvention should only be limited by the following claims and their legalequivalents.

1. An illumination device for use with a product inspection machine, said product inspection machine being used in conjunction with a product conveyor, said product conveyor directing said products through said illumination device, said product inspection machine having at least one photodetector, said photodetector having a vertical field of vision, said illumination device comprising: at least one horizontally-disposed product illumination assembly, said at least one horizontally-disposed product illumination assembly having a horizontally disposed first array of semiconductor light sources, said first array of semiconductor light sources having a repeated sequence of at least two wavelengths emittable by said semiconductor light sources, the semiconductor light sources of at least one of said at least two wavelengths of said semiconductor light sources of said first array of semiconductor light sources configured to pulsedly illuminate a scanline among at least two wavelengths, said scanline located between a first edge and a second edge of said illumination device and aligned with said photodetector vertical field of vision, said at least one horizontally-disposed product illumination assembly having a horizontally disposed second array of semiconductor light sources, said second array of semiconductor light sources having a repeated sequence of at least two wavelengths emittable by said semiconductor light sources, the semiconductor light sources of at least one of said at least two wavelengths of said semiconductor light sources of said second array of semiconductor light sources configured to pulsedly illuminate said scanline among said at least two wavelengths, said at least one horizontally-disposed product illumination assembly having a viewport therethrough, at least one of said at least one photodetectors imaging said products at said scanline through said viewport, at least one horizontally-disposed background assembly, said at least one horizontally-disposed background assembly sufficiently distant said at least one horizontally-disposed product illumination assembly to permit said products to pass therethrough, said at least one horizontally-disposed background assembly having an inner surface, said inner surface of said at least one horizontally-disposed background assembly having a background surface aligned with said viewport and said scanline, said background surface having height at least equal to said vertical field of vision of said photodetector at said inner surface, said at least one horizontally-disposed background assembly having at least one horizontally disposed background array of semiconductor light sources, said background array of semiconductor light sources having a repeated sequence of at least two wavelengths emittable by said semiconductor light sources, said repeated sequence of at least two wavelengths of semiconductor light sources identical in wavelength emission to the combination of said first array of semiconductor light sources and said second array of semiconductor light sources, and the semiconductor light sources of at least one of said at least two wavelengths of said semiconductor light sources of said background array of semiconductor light sources configured to pulsedly illuminate said background surface among said at least two wavelengths.
 2. The illumination device of claim 1, wherein the intensity of said semiconductor light sources of said at least one of said at least two wavelengths of said semiconductor light sources of said first array of semiconductor light sources configured to pulsedly illuminate a scanline and the semiconductor light sources of at least one of said at least two wavelengths of said semiconductor light sources of said background array of semiconductor light sources configured to pulsedly illuminate said background surface are uniform and instantaneously adjustable.
 3. The illumination device of claim 2, wherein said semiconductor light sources are light-emitting diodes.
 4. The illumination device of claim 3, wherein: the width of said at least one horizontally-disposed background assembly is equivalent to the width of at least one horizontally-disposed product illumination assembly, one of said at least one horizontally-disposed background assembly is contained within each of said at least one horizontally-disposed product illumination assembly and two of said at least one horizontally-disposed product illumination assembly are oppositely positioned.
 5. The illumination device of claim 4, wherein: said product conveyor has width, the width of said at least one horizontally-disposed product illumination assembly is greater than said width of said product conveyor.
 6. The illumination device of claim 5, wherein said product inspection machine is a machine vision sorting machine.
 7. The illumination device of claim 4, wherein said product inspection machine is a machine vision sorting machine.
 8. An illumination device for use with a product inspection machine, comprising: at least one horizontally-disposed product illumination assembly, said at least one horizontally-disposed product illumination assembly having a horizontally disposed first array of semiconductor light sources, said first array of semiconductor light sources having a repeated wavelength-emission sequence of at least two wavelengths emittable by said semiconductor light sources, the semiconductor light sources of at least one of said at least two wavelengths of said semiconductor light sources of said first array of semiconductor light sources configured to pulsedly illuminate a scanline, said scanline located between a first edge and a second edge of said illumination device and aligned with said photodetector vertical field of vision, the intensity of the semiconductor light sources of at least one wavelength of said at least two wavelengths of semiconductor light sources of said first array of semiconductor light sources being instantly controllable, said at least one horizontally-disposed product illumination assembly having a horizontally disposed second array of semiconductor light sources, said second array of semiconductor light sources having a repeated wavelength-emission sequence of at least two wavelengths emittable by semiconductor light sources, the semiconductor light sources of at least one of said at least two wavelengths of said semiconductor light sources of said second array of semiconductor light sources illuminating said scanline, the intensity of the semiconductor light sources of at least one wavelength of said at least two wavelengths of semiconductor light sources of said second array of semiconductor light sources being instantly controllable, said at least one horizontally-disposed product illumination assembly having a viewport therethrough, at least one horizontally-disposed background assembly, said at least one horizontally-disposed background assembly having an inner surface, said inner surface of said at least one horizontally-disposed background assembly having a background surface aligned with said viewport and said scanline, said at least one horizontally-disposed background assembly having at least one horizontally disposed background array of semiconductor light sources, said background array of semiconductor light sources having a repeated wavelength-emission sequence of at least two wavelengths emittable by said semiconductor light sources, said repeated sequence of at least two wavelengths of semiconductor light sources identical in wavelength emission to the combination of said first array of semiconductor light sources and said second array of semiconductor light sources, the intensity of the semiconductor light sources of at least one infrared wavelength of said at least one infrared wavelength of semiconductor light sources of said second array of semiconductor light sources being instantly controllable and equivalent to the intensity of the corresponding semiconductor light sources of the same at least one infrared wavelength of said first array of semiconductor light sources and said at least one infrared wavelength of said second array of semiconductor light sources, the semiconductor light sources of at least one of said at least two wavelengths of said semiconductor light sources of said background array of semiconductor light sources configured to pulsedly illuminate said background surface.
 9. The illumination device of claim 8, wherein said semiconductor light sources are light-emitting diodes.
 10. The illumination device of claim 9, wherein said product inspection machine is a machine vision sorting machine.
 11. The illumination device of claim 8, wherein said product inspection machine is a machine vision sorting machine.
 12. A method for inspecting product with a single photodetector, said photodetector having a camera integration time sufficient to integrate successive frames to obtain a satisfactory signal to noise ratio, comprising: permitting said product to free fall into an illumination device, said illumination device comprising a product illumination assembly and a background assembly; illuminating said product for at least said camera integration time at a scanline with light of a first wavelength from at least one array of semiconductor light sources, said product-illuminating semiconductor light sources arranged in a repeated wavelength-emitting sequence; illuminating concurrently only a background with light of a first wavelength from a background array of semiconductor light sources, said background-illuminating semiconductor light sources arranged in a repeated wavelength-emitting sequence; capturing image data of such product at said scanline against said background under said first wavelength from a viewport with said single photodetector, said viewport aligned with said scanline and said background; transmitting said image data under said first wavelength to a processor; illuminating said product for at least said camera integration time at a scanline with light of a second wavelength from said at least one array; illuminating concurrently only said background with light of a second wavelength from a said background array; capturing image data of such product at said scanline against said background under said second wavelength from said viewport with said single photodetector; transmitting said image data under said second wavelength to said processor; determining by said processor if said product is within a range of acceptable levels; signaling an ejector to deflect said product determined to be outside said range of acceptable levels. 